Torsion pit prop



June 16, 1959 R. T.YVOGEL 2,890,854

TORSION PIT PROP Filed Jan. 3, 1957 3 Sheets-Sheet 1 & mun-K INVENTOR RUDOL F V0651.

'I'TORNEY June 16, 1959 RT. VOGEL 2,890,854

' TORSION PIT PROP INVENTOR RUDOLF VOGEL 2 ATTORNEYS June 16, 1959 R. T. VOGEL 2,890,354

- TORSION PIT PROP Filed Jan. 3, 1957 3 Sheets-Sheet 3 I A W Has v INVENTOR FIG. 7

R000 VOGEL ATTORNEYS United States Patent TORSION PIT PROP Rudolf T. Vogel, Oberhausen-Sterkrade, Germany, assignor to Gutehoifnungshutte Sterkrade Aktiengesellschaft, Oberhausen-Sterkrade, Germany Application January 3, 1957, Serial No. 632,285

Claims priority, application Germany January 9, 1956 9 Claims. (Cl. 248-356) The present invention relates broadly to the art of supporting means or stanchions.

More particularly, the invention relates to stanchions or props utilized in shoring up the roofs of mines. In other words, the invention relates to a mine stanchion or a prop commonly called a pit prop.

The invention specifically relates to such a prop or strut-like supporting device which while particularly adaptable for use in supporting roofs in mines, is not limited to such use, but can be utilized as a prop or support for holding up part of a building structure during erection, rebuilding, or repair.

The invention is still more specifically related to such props or upright supporting means of the multipartite type including two component parts telescopically related one inside the other so that one part can be extended to reach a roof or other surface that is to be supported and in which means are provided to frictionally secure one part to the other so that such means, usually termed a prop lock or clamp, can support the load to be supported. Usually the clamping means must be such that a frictional clamping action supports the load to be supported.

The prior art has proposed various constructions for the clamping means of multipartite props because the clamping means is a very important part of the prop or stanchion and the usefulness of the prop or stanchion is predicated upon Whether or not the clamping means is suitable for all practical requirements. Of the many types of clamping means heretofore proposed, those which constitute wedge systems have been most extensively utilized, particularly in mining practices prevalent in Germany. It has been found, however, that the so-called wedge systems heretofore used do not constitute an ideal solution that fully answers all problems concerned with a prop clamping means because the efficiency of such systems, that is, the ratio between the energy which has to be expended or used in clamping and the frictional force to be produced as a result thereof, leaves much to be desired. A considerable proportion, generally far more than half of the energy used in effecting clamping, has to be regarded as lost and is actually wasted by the inevitable friction which arises between the parts of a wedge mechanism. It, therefore, follows that any particular prop utilizing a Wedge system requires the expenditure of an undesirably high amount of energy for clamping purposes in order to obtain the particular supporting capacity required. Additionally, a further disadvantage arises which is based on the loss of energy during clamping. As revealed in practice, there is a considerable percentage of frictional loss within the wedge mechanism which imposes a limit on a utilizable clamping force which can be achieved in clamping together the parts of the prop. Due to the heavy frictional losses, the force that acts externally on the clamping means and wedge system must be considerably greater than the useful clamping force created so that yielding of the clamping means or even of the prop structure per se is likely to happen if the force applied to the clamping means is unduly increased.

It is, therefore, an object of the present invention to provide a clamping means for multipartite props or stanchions which can be readily manufactured and overcome the disadvantages of prior known wedge systems.

It is a further object of this invention to provide a pit prop or a strut-like supporting device which includes at least two relatively movable torsional clamping members operative to apply clamping force to the prop by applying to the clamping members torsional moments of opposite sense or direction about the longitudinal axis of the prop or strut.

The force used for applying or initiating the torsional moments is advantageous in applying a clamping force since the normal and frictional forces produced in connection therewith, without any undesirable losses, imparts a supporting capacity to the prop with comparatively small clamping forces, that is, torsional moments, in comparison to the amount of energy that would have to be expended to impart the same supporting capacity to a prop utilizing previously known wedge systems. For example, if in using a known wedge system, it were necessary to apply three powerful hammer blows to the wedge to obtain a given supporting capacity, then using the torsional clamping arrangement of the invention, only one, quite moderate, hammer blow will provide the same supporting capacity. As a result, those who utilize the teaching of this invention, for example, a miner, have their work markedly facilitated resulting in a saving of energy and time which can hardly be underestimated in view of the physical and mental strain imposed on a miner during his work.

Further, a torsional clamping system as proposed by the invention is distinguished from wedge systems by another important advantage in that the system of this invention avoids imparting a bending stress to the parts of a prop which are to be clamped together or to the parts of the clamping means per se so that the presently known disadvantages arising from bending stresses are avoided. In many pit prop arrangements previously proposed, on yielding of the upper part of the prop, as a result of bending stresses, the prop clamp or lock may be moved to released position so that the supporting capacity of the prop or strut means drops considerably and often quite suddenly.

It is, therefore, a specific object of the present invention to provide a pit prop or strut-like supporting means including upper and lower parts telescopically related to one another and including clamping or locking means to secure one part in adjusted position in relation to the other and which incorporates means for applying a clamping force as a result of applying torsional moments in opposite directions about the longitudinal axis of the prop.

The supporting and fundamental advantages of the present invention are, in themselves, independent of the. specific and detailed construction of particular torsional clamping means. In order to obtain a simple and robust construction, particularly useful in supporting the roofs of mines, it is advisable to provide clamping means including two rings adapted to surround one prop part with each ring including a projection or lateral extension on its outer periphery for receiving a clamping force applied, for example, by means of a wedge. It is possible to utilize either a vertically or a horizontally acting wedge. While it may be true that the friction of the wedge against the torque transmitting ring is a waste friction which would adversely affect efficiency, the resulting loss remains within such moderate limits that .its does not in any way diminish the superiority of the torsional clamping principle as compared with previously proposed clamping systems for such purposes.

The frictional forces produced by the torsional moments through the medium of normal forces, are dependent on the nature of the surfaces to be clamped together, that is to say, on the coefficient of friction. Therefore, it is advisable to provide friction inserts. If the upper part of a pit prop is triangular, square or of other polygonal section, such friction inserts may be disposed to one side of the center of the sides of the polygon preferably offset toward the corners.

It is, therefore, a further object of the present invention to provide a torsional clamping arrangement for multipartite props including at least two rings having similar internal polygonal sections and in which friction inserts are disposed between the inner periphery of the rings and the outer periphery of a correspondingly shaped, but smaller, prop part with the inserts offset with respect to the centers of the sides of the prop part. With regard to manufacturing accuracy, it is sufficient that the friction inserts mounted within the rings, are in alignment with one another.

Further and more specific objects will be apparent from the following description taken in connection with the accompanying drawings illustrating several forms of the torsional clamping arrangement for multipartite props or strut-like supporting means and in which:

Figure 1 is a perspective view of a portion of a multipartite pit prop or strut-like supporting means incorporating one form of a torsional clamping arrangement,

Figure 2 is a fragmentary view in perspective with parts broken away and partly in section illustrating another modification of the invention,

Figure 3 is a longitudinal sectional view taken along lines 3-3 of Figure 2,

Figures 4 and 5 are cross sectional views taken along lines 4-4 and 5-5 respectively of Figure 3,

Figure 6 is a cross sectional view similar to Figure 4, but illustrating another form of the invention utilizing a horizontally acting wedge for applying the torsional moments, and,

Figures 7 and 8 are diagrammatic views illustrating the utilization of the clamping force in accordance with the teaching of the invention and in accordance with previously known wedge systems respectively.

The form of pit prop or stanchion illustrated in Figure 1 includes an upper hollow component or part 1 of rectangular cross section and a lower tubular part 2 into which the upper part can slide telescopically. Mounted for association between the upper and lower parts are three ring members including end rings 3a and 3b and an intermediate ring 4. Each of these rings has a rectangular inner periphery substantially corresponding to, but larger than, the outer periphery of the upper part 1. Projecting laterally from the outer periphery of the rings are projections 5a, 5b and 6 respectively. These projections are similarly arranged on the two end rings, but the projection 6 on the intermediate ring 4 is arranged opposite to the other two projections. The facing surface of the projections are inclined as illustrated so that by inserting a clamping wedge 7 from above, the downward movement thereof applies opposite torsional moments to the rings with the projections 5a and 5b tending to move to the right (Figure 1) whereas the projection 6 tends to move to the left. Thus, by applying a downward force to wedge 7, the opposed torsional moments fr-ictionally clamp the rings on the inner prop-part 1 which is supported in vertically adjusted position with respect to the outer part 2 by means of the lowermost ring 3b resting on the outer part. If desired, this ring can be fastened to the inner end of the outer part 2 by welding or other suitable means. In any case, a frictional locking effect is obtained by means of the clamping arrangement in such a manner that the inner part 1 yields when the load to be supported, for instance the load of the mine roof, exceeds a predetermined maximum value and thus overcomes the frictional resistance between the rings and the inner part 1.

Friction inserts 8a, 8b and 9 are secured to the inner walls of the respective rings. These friction inserts are laterally offset toward one corner of the respective sides of the upper part 1 as shown. In other words, the mserts 8a and 8b are offset to the right with regards to the axis of the part 1 and the inner sides of the clamping rings 3a and 3b whereas the inserts 9 are offset to the left. The offsetting of the friction inserts ensures that the normal forces generated by the torsional moments act at those points of the hollow upper part 1 at which it is most resistant to deformation. The further the friction inserts are displaced toward the middle of the respective sides of the upper part, the greater is the bending stress applied to the individual sides of the rectangular hollow part.

The frictional inserts consist of metal or any other convenient material having a preferred coeificient of friction.

As previously indicated, instead of the lower ring merely resting on the top of the lower part 2, the upper and lower rings may be connected to the lower part of the prop or .be integral with it. Figure 2 discloses a modification in which the lower ring member 3b is an integral part of the lower prop-part 2. An upper ring member 3a is welded as at 12 to the lower ring formation on the prop part 2 so that instead of two separate projections as is the case in Figure 1, a single lateral projection 5 is provided. The intermediate ring 4' is smaller in outer diameter as compared with the upper ring and is disposed in a groove 11 provided between facing shoulders 13 and 14 of the upper and lower rings as shown in Figure 3. The inner rectangular opening of the three ring parts 3a, 3b and 4' is the same size and friction inserts 8a, 8b and 9' are arranged in the same fashion as in Figure 1. There is also a projection 6' extending laterally from the outer periphery of ring 4' through a suitable opening 6A provided in the exterior of the respective ring parts 3a and 3b as shown in Figure 4. As a result of the rigid connection between the ring members 3a and 3b and the lower part 2, the upper prop-part 1 and the lower prop-part 2' are braced relative to one another by the torsional clamping arrangement and the load resting on upper prop-part 1 is transmitted to the lower prop-part 2 solely by means of a frictional locking effect of the torsional clamping arrangement without there being any supporting bearing pressure between the lower ring and the lower prop-part, as is the case in Figure 1. Thus, the middle ring 4 does not need to rest on the lower ring part 3b when the clamping device is applied. In order to reduce friction between the middle ring 4 and the outer ring parts 3a and 3b when the torsional clamping is being applied, the middle ring can have a coating of lubricating grease on its opposite end faces. The middle clamping ring rests on the upper surface of lower ring part 3b when the upper prop-part sinks under the load to be supported overcoming the frictional resistance between the two propparts which are clamped together by means of the clamping torque. Accordingly, a coating of lubricating grease can also be applied to the end faces of ring 4 in the form illustrated in Figure 1.

Otherwise, the use and operation of the forms of the invention shown in Figures 2 to 4 is the same as in Figure 1. The two forms are identical in principle in that the upper prop-part is not displaced laterally in relation to the clamp members during clamping because the normal forces are produced solely by a torque. Conse quently, in direct contrast to any wedge clamping systerns, the wear of the friction inserts is of no consequence because the prop-parts are not laterally displaced relative to one another. To obtain torsional clamping, it is not absolutely essential to have two rings, such as 3a and 3b in Figure 1. However, for structural reasons it is advisable to provide three clamping rings, the upper and lower rings 3a and 3b or their corresponding components 3a and 3b in Figure 2 provides a sufficient internal hearing and guiding of the upper prop-part 1 before clamping so that this upper prop-part is prevented from inclining laterally on sinking or settling under load of the prop proper.

The more effective utilization of clamping forces in the present invention as compared with the aforementioned wedge systems is illustrated diagrammatically in Figures 7 and 8. If a clamping force S is employed in a wedge system, Figure 8, and an upper prop-part is rectangular, then the resulting supporting capacity with a coeflicient of friction U is:

so that a= +.2 Q1 b This ratio is 2 when and 3 when a=b.

Thus, the supporting capacity can be increased considerably according to the selection of the lever arms a and b. The transmission ratio embodied in the principle of the torsional clamping arrangement of the invention is clearly and fundamentally independent of the cross sectional shape of the upper and lower prop-parts. It applies equally well, for ex ample, with hexagonal sections, with an out-of-round, that is, oval section and also with a circular section if this is provided on its outer periphery with longitudinal strips or ribs for the reception of the normal forces. That is, if the outer periphery of the inner prop-part is round and provided with longitudinal ribs and the shape of the interior of the clamping rings is also ribbed. In some circumstances, a transmission ratio even more favorable than that set forth above may be obtained with cross sectional shapes other than rectangular ones. Additionally, it is not necessary that the wedge used to apply the torsional clamping forces be a vertically acting wedge as shown in the forms of Figures 1 and 2. Figure 6 illustrates a modification in which a horizontal wedge is utilized. In this form of the invention, the intermediate ring 4 is provided with a projection 6" that has an aperture therein and the other rings include a projection 5" provided with an aperture through which is passed the projection 6". A horizontal wedge 10' is used to apply the clamping forces.

It is also possible to apply the clamping force to the clamp rings by other means, such as, a toggle-lever system, or by pneumatically or hydraulically actuated means.

The manufacture of the clamp rings does not require substantial accuracy, since the inner faces of the rings do not have to be in vertical alignment so long as the inner faces of the friction inserts 8a, 8b and 9 lie in a common plane along each side of the upper prop-part. Thus, the manufacture can be effected by stacking rings one above the other and after mounting the friction inserts on the interior of the respective rings pass a broach through the interior so that the cross section comprised between the inner faces of the respective friction inserts is the same for each ring.

It is, therefore, clear that the invention has provided an improved pit prop arrangement in which an inner part that is telescopically related to the outer part can be braced thereto in vertically adjusted relation and in which the clamping is effected by frictionally engaging the exterior of the inner part by. applying opposite torsional moments to at least two clamping members with torque being applied in opposite directions about the longitudinal axis of the prop-part.

What is claimed is:

1. In a strut-like supporting device at least two elongated members mounted for axial movement relative to one another so that the effective length of the device can be adjusted, one of said members being of noncircular cross section, and torsional clamping means operatively associated between the members including components for frictionally engaging at least one of the members including at least two rigid torsional clamping elements and means for applying torque to said elements in respective opposite directions about the longitudinal axis of the member being of non-circular cross section thereby applying to said member of non-circular cross section torsion moments acting in opposite directions producing a frictional locking efiect.

2. A strut-like supporting device comprising an outer part, an inner part telescopically related to the outer part for adjusting movement therein so as to adjust the effective length of the device, the inner part being of noncircular cross section, and clamping means operatively associated between the two parts for bracing the inner part in adjusted position to the outer part, said clamping means comprising at least two rigid torsional clamping members adapted for frictional engagement with at least the inner part and means for applying torque to the respective clamping members in opposite directions respectively about the longitudinal axis of the inner part thereby applying to such pant torsion moments acting in opposite directions producing a frictional locking effect.

3. A strut-like supporting device as claimed in claim 2 in which said torsional clamping members: comprise ring means disposed around said inner part, each ring means having a laterally extending projection, said projections being circumferentially spaced and including facing wedge accommodating surfaces and wedge means movable between the projeotions for applying torque to the ring members acting in opposite directions about the longitudinal axis of the inner part.

4. A strut-like supporting device as claimed in claim 2 in which said clamping members include a first member adapted to receive torque in one direction and two additional clamping members, one on each side of said first member and adapted to receive torque in an opposite direction.

5. A strut-like supporting device as claimed in claim 2 in which the inner part has a polygonal shape, said clamping members surrounding said inner part and having inner sides corresponding in number to the number of sides of the inner part and friction inserts disposed between the respective clamping members and the sides of the inner part and said inserts being mounted to one side of the center of the respective sides of the inner part.

6. A strut-like supporting device as claimed in claim 2 and means securing one of said clamping members to the outer part and said other clamping member being movable with respect to said one clamping member.

7. In a strut-like supporting device, such as a pit prop of the type in which an outer hollow prop member telescopically receives an inner prop member of non-circular cross section, the improvement comprising means for bracing the inner prop member to the outer member in selected axially adjusted positions including at least two ring means surrounding the inner member and supported by the outer member, each ring means having a projection extending laterally thereof, said projections including spaced surfaces and means for applying forces to said surfaces in opposite directions to apply torque to said ring means acting in opposite directions about the axis of the inner prop member to torsionally clamp the ring means to the inner prop member.

8. A pit prop including an outer elongated tubular member, an inner elongated tubular member of polygonal cross section telescopically related Within the outer member, at least two ring members surrounding said inner member and including inner surfaces corresponding in number to the number of sides of the inner member, friction inserts disposed between the exterior sides of the inner member and the adjacent surfaces of the respective ring means, said inserts being mounted to one side of the center of the respective sides of the inner member,

each ring means having a projection extending outwardly 25 thereof, the projections including oppositely directed surfaces and means cooperable with the projections for applying torque forces thereto acting in opposite directions about the longitudinal axis of the inner member to torsionally clamp the ring means to the inner member in adjusted relation of the inner member with respect to the outer member.

9. A pit prop as claimed in claim 8 in which one of said ring means includes an inwardly directed shoulder on the interior of the outer member, said outer member having an aperture therethrough, another ring member having less external transverse dimensions than the outer member and seated on the shoulder of the outer member and including a lateral projection extending through said aperture and facing the projections of said ring means, the last named projections being secured together and at least one of said first named ring members being secured to the outer member.

References Cited in the file of this patent UNITED STATES PATENTS 485,463 Ennis Nov. 1, 1892 1,273,811 Bell July 30, 1918 1,978,865 Haines Oct. 30, 1934 2,251,253 Miller July 29, 1941 FOREIGN PATENTS 632,897 France Oct. 17, 1927 580,843 Germany July 17, 1933 

